A young black girl is on her way to school when her sister's husband chases her on a horse. He sneaks off the horse and grabs her and he pulls her into the woods as he tries to rape her. Offscreen you hear him go "UH!" and stumble out of the bushes after her holding his crotch. Clip: http://femdomspace.com/videos/play/femdomspace/9689/the-color-purple-1985-offscreen-ballbusting-by-schoolgirl

This one's tough to find, but it's a great
scene. Ursula Andress, as a secret agent, runs into a horny guy in
the
hallway who's interrupting her mission. Feeling his state of arousal,
but knowing she can't be diverted, she says, 'It's a
shame to
waste this, but...' and knees him really hard. He goes down just like you
or I would in real life (and stays down).
Plus, Ursula was a young
woman (38) and looked really hot!< Ursula Andress did not appear in Colt
45. The actual title to this film is 'Colpo In Canna' aka 'Loaded
Guns'. (Since I originally posted the description of this scene, I must
say that the last comment is absolutely correct; the movie is 'Loaded
Guns', but the scene is still great)
Probably my favorite. The first one is about half way through the movie, Ursula has to get past this muscled guard. She sprays something in his face and moves on to whatever room it is. A moment later she is back and he is awake, so she comes onto him and whispers sweet things into his ear. Very suddenly: her body tightens, her arms are raised, a flash of knee between the legs and her fists come down on his head. She bends over to mock comfort him and we get a good look at her breasts and legs (slit skirt). Great for her sweet voice, the sudden viciousness of the attack and the titillating aftermath. You'll have to play it in slo-mo to see how realistic (or not) the knee is. 2) About 10 minutes from the end, she is corned by Woody Strode who pulls a gun on her. She distracts him and kicks him in the nuts, believe this is off screen. The first one is the best.
**third commenter**: yes, the knee described is also one of my favourite of all times. The knee, and also another (partial) kick/bust, can partly be seen here: http://www.youtube.com/watch?v=q7VfYSretao .
But as described, what makes the scene as great as it is, is the atmosphere that precedes and follows it, so I would recommend getting hold of this movie because youtube doesn't make justice to it.
Hell, that knee sucks
watch it and check
55:52
http://www.youtube.com/watch?v=1XWZ6sz449o
but the movie is cool, she is naked there)

Happens about 43:30 into the movie...2 kicks,one knee to the stomach as the guy goes down. ALSO, on the deleted scenes on DVD, she does the same double kick to the same guy, at a slightly better angle.